Network Working Group                                             N. So
Internet Draft                                                 A. Malis
Intended Status: Informational                               D. McDysan
Expires: April 2011                                             Verizon
                                                                L. Yong
                                                                 Huawei
                                                              F. Jounay
                                                         France Telecom
                                                              Y. Kamite
                                                                    NTT
                                                       October 20, 2010



     Composite Link Framework in Multi Protocol Label Switching (MPLS)
                    draft-so-yong-rtgwg-cl-framework-02


Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with
   the provisions of BCP 78 and BCP 79.

   This Internet-Draft is submitted to IETF in full conformance with
   the provisions of BCP 78 and BCP 79. This document may not be
   modified, and derivative works of it may not be created, and it may
   not be published except as an Internet-Draft.

   This Internet-Draft is submitted to IETF in full conformance with
   the provisions of BCP 78 and BCP 79. This document may not be
   modified, and derivative works of it may not be created, except to
   publish it as an RFC and to translate it into languages other than
   English.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008. The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other documents



So, et al.                Expires April 2011                   [Page 1]


Internet-Draft        Composite Link Framework           October 2010


   at any time.  It is inappropriate to use Internet-Drafts as
   reference material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

   This Internet-Draft will expire on April 20, 2011.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with
   respect to this document.

Abstract

   This document specifies a composite link framework in MPLS network.
   A composite link consists of a group of homogenous or non-homogenous
   links that have the same forward adjacency and can be considered as
   a single TE link or an IP link in routing. The composite link relies
   on its component links to carry the traffic over composite link. The
   document specifies composite link model. Applicability is described
   for a single pair of MPLS-capable nodes, a sequence of MPLS-capable
   nodes, or a set of layer networks connecting MPLS-capable nodes.

Table of Contents

   1. Introduction...................................................3
   2. Conventions used in this document..............................3
      2.1. Terminology...............................................3
   3. Composite Link Framework.......................................4
   4. Composite Link in Control Plane................................5
   5. Composite Link in Data Plane...................................6
   6. Security Considerations........................................7
   7. IANA Considerations............................................7
   8. References.....................................................7
      8.1. Normative References......................................7
      8.2. Informative References....................................7
   9. Acknowledgments................................................7






So, et al.                Expires April 2011                  [Page 2]


Internet-Draft        Composite Link Framework           October 2010


1. Introduction

   Composite link functional requirement are specified in [CL-REQ].
   This document specifies a framework of Composite Link in IP/MPLS
   network to meet the requirements. Single link and link bundle
   [RFC4201] have been widely used in today's IP/MPLS networks. A link
   bundle bundles a group of homogeneous links as a TE link to make
   routing approach more scalable. A composite link allows bundling
   non-homogenous links together as a single logical link. The
   motivations for using a composite link are descried in the document
   [CL-REQ]. This document describes composite link framework in the
   context of MPLS network with MPLS control plane.

   A composite link is a single logical link in MPLS network that
   contains multiple parallel component links between two routers.
   Unlike a link bundle [RFC4201], the component links in a composite
   link can have different properties such as cost or capacity. A
   composite link can transport aggregated traffic as other physical
   links from the network perspective and use its component links to
   carry the traffic internally.

   Specific protocol solutions are outside the scope of this document.



2. Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2.1. Terminology

   Composite Link: a group of component links, which can be considered
   as a single MPLS TE link or as a single IP link used for MPLS.

   Component Link: a physical link (e.g., Lambda, Ethernet PHY, SONET/
   SDH, OTN, etc.) with packet transport capability, or a logical link
   (e.g., MPLS LSP, Ethernet VLAN, MPLS-TP LSP, etc.)

   Traffic Flow: A set of packets with a common identifier and
   characteristics that is used by Composite link interior functions to
   place the set of packets on the same component link. Identifiers can
   be an MPLS label stack or any combination of IP addresses and
   protocol types for routing, signaling, and management packets.

   Virtual Interface: Composite link is advertised as an interface in
   IGP






So, et al.                Expires April 2011                  [Page 3]


Internet-Draft        Composite Link Framework           October 2010


3. Composite Link Framework

   A Composite Link in the context of MPLS network is a set of parallel
   links between two routers that form a single logical link within the
   network. Composite link model is illustrated in Figure 1, where a
   composite link is configured between routers R1 and R2.  The
   composite link has three component links.  Individual component
   links in a composite link may be supported by different transport
   technologies such as wavelength, Ethernet VLAN.  Even if the
   transport technology implementing the component links is identical,
   the characteristics (e.g., bandwidth, latency) of the component
   links may differ.

   As shown in Figure 1, the composite link may carry LSP traffic flows
   and control plane packets. A LSP may be established over the link by
   either RSVP-TE or LDP signaling protocols. All component links in a
   composite link have the same forwarding adjacency. The composite
   link forms one routing interface at the composite link end points
   for MPLS control plane. In other words, two routers connected via a
   composite link have forwarding adjacency and routing adjacency. Each
   component link only has significance to the composite link, i.e. it
   does not appear as a link in the control plane.

              Management Plane
          Configuration and Measurement <------------+
                     ^                               |
                     |                               |
             +-------+-+                           +-+-------+
             |       | |                           | |       |
        CP Packets   V |                           | V     CP Packets
             |  V    | |     Component Link 1      | |    ^  |
             |  |    |=|===========================|=|    |  |
             |  +----| |     Component Link 2      | |----+  |
             |       |=|===========================|=|       |
   Aggregated LSPs   | |                           | |       |
            ~|~~~~~~>| |     Component Link 3      | |~~~~>~~|~~
             |       |=|===========================|=|       |
             |       | |                           | |       |
             | LSR     |                           |    LSR  |
             +---------+                           +---------+
                     !                               !
                     !                               !
                     !<------ Composite Link ------->!


                Figure 1  Composite Link Architecture Model

   A component link in a composite link may be constructed in different
   ways.[CL-REQ] Figure 2 shows three common ways that may be deployed
   in a network.




So, et al.                Expires April 2011                  [Page 4]


Internet-Draft        Composite Link Framework           October 2010


      +-------+                 1. Physical Link             +-------+
      |     |-|----------------------------------------------|-|     |
      |     | |                                              | |     |
      |     | |     +------+                     +------+    | |     |
      |     | |     | MPLS |    2. Logical Link  | MPLS |    | |     |
      |     |.|.... |......|.....................|......|....|.|     |
      |     | |-----|  R3  |---------------------|  R4  |----| |     |
      |     | |     +------+                     +------+    | |     |
      |     | |                                              | |     |
      |     | |                                              | |     |
      |     | |     +------+                     +------+    | |     |
      |     | |     |GMPLS |    3. Logical Link  |GMPLS |    | |     |
      |     |.|. ...|......|.....................|......|....|.|     |
      |     | |-----|  R5  |---------------------|  R6  |----| |     |
      |       |     +------+                     +------+    |       |
      | R1    |                                              |    R2 |
      +-------+                                              +-------+
            |<------------- Composite Link ------------------->|

             Figure 2 Illustration of Component Link Variances

   As shown, the first component link is configured with direct
   physical media wire. The second component link is a TE tunnel that
   traverses R3 and R4. Both R3 and R4 are the nodes in the MPLS. The
   third component link is formed by lower layer network that has GMPLS
   enabled. In this case, R5 and R6 are not the nodes controlled by the
   MPLS but provide the connectivity for the component link.

   Composite link forms one logical link between connected routers and
   is used to carry aggregated traffic.[CL-REQ] Composite link relies
   on its component links to carry the traffic over the composite link.
   This means that a composite link maps incoming traffic into
   component links. At the transmitting end (R1 in Figure 1), composite
   link maps a set of traffic flows including control plane packets to
   a specific component link.  At the receiving end (R2 in Figure 1),
   composite link receives the packets from its component links and
   sends them to MPLS forwarding engine like a regular link.

   Traffic mapping to component links may be done by control plane,
   management plane, or data plane.[CL-REQ] The objective is to keep
   the individual flow packets in sequence and do not overload any
   component link.[CL-REQ] Operator may have other objectives such as
   load balance over component links. A flow may be a LSP, or sub-LSP
   [MLSP], PW, a flow within PW [FAT-PW], entropy flow in LSP
   [Entropy].

4. Composite Link in Control Plane

   A composite Link is advertised as a single logical interface between
   two connected routers, which forms routing and forwarding adjacency
   between the routers in IGP. The interface parameters for the
   composite link can be pre-configured by operator or be derived from


So, et al.                Expires April 2011                  [Page 5]


Internet-Draft        Composite Link Framework           October 2010


   its component links. Composite link advertisement requirements are
   specified in [CL-REQ].

   In IGP-TE, a composite link is advertised as a single TE link
   between two connected routers. This is similar to a link bundle
   [RFC4201]. Link bundle applies to a set of homogenous component
   links. Composite link allows homogenous and non-homogenous component
   links. The link bundle protocol extension for composite link
   advertisement is for further study.

   Both LDP [RFC5036] and RSVP-TE [RFC3209] can be used to signal a LSP
   over a composite link. Since composite link capacity is aggregated
   capacity and is often larger than individual component link
   capacity, it is possible to signal a LSP whose BW is larger than
   individual component link capacity.[CL-REQ] Assumption is such LSP
   carrying an aggregated traffic.

   A composite link may contain the set of component links. A component
   link may be configured by operator or signaled by the control plane.
   In both cases, it is necessary to convey component link parameters
   to the composite link.[CL-REQ]

   When a component link is supported by lower layer network (third
   component link in figure 2), the control plane that the composite
   link resides is able to interoperate with the GMPLS or MPLS-TP
   control plane that lower layer network uses for component link
   addition and deletion. [CL-REQ]

5.  Composite Link in Data Plane

   Composite link may appear as one single interface or multiple
   interfaces in data plane.

   The traffic over composite link is distributed over individual
   component links. Traffic dissemination may be determined by control
   plane, management plane, or data plane, and may be changed due to
   component link status change.[CL-REQ]

   A component link in a composite link may fail independently. The
   composite link functions are able to recognize component link
   failure and re-assign impacted flows to other active component links
   in minimal disruptive manner. When a composite link can't recover
   some impacted flows, it notifies control plane about the flows. When
   a composite link is not able to transport all flows, it preempts
   some flows based upon local management configuration and informs the
   control plane on these preempted flows. This action ensures the
   remaining traffic is transported properly.

   The composite link functions provide component link fault
   notification and composite link fault notification. Component link
   fault notification is sent to the management plane. Composite link
   fault notification is sent to the control plane and management


So, et al.                Expires April 2011                  [Page 6]


Internet-Draft        Composite Link Framework           October 2010


   plane. Composite link allows operator to trace which component link
   a LSP is assigned to.

6. Security Considerations

   For further study.

7. IANA Considerations

   IANA actions to provide solutions are for further study.

8. References

8.1. Normative References

   [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
   Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3209]  D. Awduche, L. Berger, D. Gan, T. Li, V. Srinivasan, G.
   Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels,"   December
   2001

   [RFC4201]  Kompella, K., "Link Bundle in MPLS Traffic Engineering",
   RFC 4201, March 2005.

   [RFC5036]  Andersson, L., "LDP Specification", RFC 5036 , October
   2007.

8.2. Informative References

   [CL-REQ] Villamizar, C. and McDysan, D, "Requirements for MPLS Over
   Composite Link", Oct. 2010, Work in Progress

   [Entropy Label] Kompella, K. and S. Amante, "The Use of Entropy
   Labels in MPLS Forwarding", November 2008, Work in Progress

   [FAT-PW] Bryan, S., et. Al, "Flow Aware Transport of Pseudowire over
   an MPLS PSN", draft-ietf-pwe3-fat-pw-04, Work in progress

   [MLSP] Kompella, K. "Multi-path Label Switched Paths Signaled Using
   RSVP-TE", draft-kompella-mpls-rsvp-ecmp-00.txt, July 2010, Work in
   Progress

9. Acknowledgments

   Authors would like to thank Adrian Farrel for his extensive comments
   and suggestions, Ron Bonica, Nabil Bitar, Eric Gray, Lou Berger, and
   Kireeti Kompella for their reviews and great suggestions.






So, et al.                Expires April 2011                  [Page 7]


Internet-Draft        Composite Link Framework           October 2010


   Authors' Addresses

      So Ning
      Verizon
      2400 N. Glem Ave.,
      Richerdson, TX  75082
      Phone: +1 972-729-7905
      Email: ning.so@verizonbusiness.com


      Andrew Malis
      Verizon
      117 West St.
      Waltham, MA  02451
      Phone: +1 781-466-2362
      Email: andrew.g.malis@verizon.com

      Dave McDysan
      Verizon
      22001 Loudoun County PKWY
      Ashburn, VA  20147
      Email: dave.mcdysan@verizon.com


      Lucy Yong
      Huawei USA
      1700 Alma Dr. Suite 500
      Plano, TX  75075
      Phone: +1 469-229-5387
      Email: lucyyong@huawei.com

      Frederic Jounay
      France Telecom
      2, avenue Pierre-Marzin
      22307 Lannion Cedex,
      FRANCE
      Email: frederic.jounay@orange-ftgroup.com

      Yuji Kamite
      NTT Communications Corporation
      Granpark Tower
      3-4-1 Shibaura, Minato-ku
      Tokyo  108-8118
      Japan
      Email: y.kamite@ntt.com









So, et al.                Expires April 2011                  [Page 8]